The present disclosure relates to flash memory back-up systems, and more specifically, to reporting defects in a flash memory back-up system.
When main power fails in a system a pre-charged standby capacitor keeps the system power on long enough for data to transfer from system memory to NAND flash memory. NAND flash memory is a type of non-volatile storage that does not require power to retain data. A flash controller system reads data from volatile memory and stores that data amongst one or more flash devices. Each distinct flash device is known as a channel.
Any such back-up mechanism must deal with and manage one of NAND flash technology's innate problems: namely, that blocks eventually wear out due to excessive program and erase cycles. As NAND flash geometries shrink this problem becomes even more severe. It is a likely possibility that the back-up mechanism will encounter one of these worn out blocks in the course of saving data and, the fact that this block is worn will not have been known prior to starting the back-up.
When one of these so-called “Grown Bad Blocks” is encountered the mechanism is expected to re-direct the data to be saved to another unworn out area of NAND flash. The mechanism should also record the position of this newly discovered bad block so that the user may be notified of its presence and can take it into account during future management or maintenance of the NAND flash memory.